In the Chair of Bridge, Metal and Timber Structures (L3) research and development works related to design, manufacture and assessment of the technical condition of various types of structures made of steel and aluminum as well as of timber and timber-based materials are conducted. They mainly concern the verification of bearing capacity and stability of such structures, extended to the estimation of the safety level guaranteed in persistent and accidental design situations, after different periods of service. A large part of the research is aimed at developing the procedures for rational evaluation of the resistance, both of the members and of the complex structural systems, under the impact of simulated fire conditions with various fire development scenarios. A separate area of activity of the chair employees lies in the broadly understood issues related to the transportation structures, mainly bridges and tunnels. Activities in this field include both advanced analyses of structural mechanics and also those related to the specialist design aspects and modern technological solutions.